This is the method I use to touch off tools, hope it helps. At home or reference position origin all. Look at the incremenal position numbers, they should be zero. Move the tool to the part and position tool at z 0.0 on the part write down that number. take a cut on the diameter write down that number, measure the part and add to the x number. Use theses numbers in a g50 line at the beginning of your program. Your tool offsets will be zero to start and you can make small adjustments from there.